An electrically powered rotary-wing aircraft with a first predetermined number of thrust producing units and a second predetermined number of batteries. Each one of the first predetermined number of thrust producing units may include a rotor, and an electrical drive unit with at least two electric motors. Each battery of the second predetermined number of batteries is coupled to at most one electric motor of the at least two electric motors of at least one of the first predetermined number of thrust producing units, and each electric motor of the at least one of the first predetermined number of thrust producing units is coupled to at most one of the second predetermined number of batteries.

An electrically powered rotary-wing aircraft with a first predetermined number of thrust producing units and a second predetermined number of batteries. Each one of the first predetermined number of thrust producing units may include a rotor, and an electrical drive unit with at least two electric motors. Each battery of the second predetermined number of batteries is coupled to at most one electric motor of the at least two electric motors of at least one of the first predetermined number of thrust producing units, and each electric motor of the at least one of the first predetermined number of thrust producing units is coupled to at most one of the second predetermined number of batteries.

The ‘Air Wheel’ rotor is a rotor with blades of variable pitch and variable twist. The ‘Air Wheel’ rotor comprises one or more hubs connected to the closed axisymmetric wing via flexible blades. There is provided a wide range of combinations of the wing relative width and coning angle typical for a lifting rotor with a thin planar wing attached to the tips of long blades, for a shrouded fan in a wide annular wing, or an impeller in a rotating cylindrical wing is provided.

The ‘Air Wheel’ rotor combines and enhances the advantages of a rotor and a wing. The ‘Air Wheel’ rotor has high aerodynamic properties, and eliminates limitations of the rotor size and flight speed. The ‘Air Wheel’ rotor can be used for designing vertical take-off and landing aircraft.

Embodiments are directed to boosting aircraft engine performance for takeoff and critical mission segments by reducing airflow used for cooling exhaust gases. The airflow is reduced by stopping an accessory blower or by closing an external air vent. Eliminating the cooling airflow to the exhaust has the effect of lowering the backpressure on the engine, which thereby increases maximum engine power.

Embodiments are directed to boosting aircraft engine performance for takeoff and critical mission segments by reducing airflow used for cooling exhaust gases. The airflow is reduced by stopping an accessory blower or by closing an external air vent. Eliminating the cooling airflow to the exhaust has the effect of lowering the backpressure on the engine, which thereby increases maximum engine power.

A configuration of a multirotor aircraft that will facilitate enhanced yaw control includes one or more adjustable members that will twist the frame of the multirotor aircraft, thereby adjusting the orientation of the motors and propellers and enhancing the yaw control of the multirotor aircraft. In some implementations, the adjustable member(s) are passive and twist in response to differential thrusts generated by the propellers. In other implementations, the adjustable members are active and twist in response to a yaw command from the multirotor aircraft control system.

A configuration of a multirotor aircraft that will facilitate enhanced yaw control includes one or more adjustable members that will twist the frame of the multirotor aircraft, thereby adjusting the orientation of the motors and propellers and enhancing the yaw control of the multirotor aircraft. In some implementations, the adjustable member(s) are passive and twist in response to differential thrusts generated by the propellers. In other implementations, the adjustable members are active and twist in response to a yaw command from the multirotor aircraft control system.

A compound helicopter includes a fuselage including a fuselage airframe, a translational thrust system coupled to the fuselage airframe and a pylon assembly subject to vibration. The pylon assembly includes a transmission and a rotor system having a main rotor assembly. The compound helicopter also includes a main rotor vibration isolation system including a plurality of augmented liquid inertia vibration eliminator units each having an isolation frequency and each coupled between the fuselage airframe and the pylon assembly to reduce transmission of the pylon assembly vibration to the fuselage airframe at the isolation frequency. Each augmented liquid inertia vibration eliminator unit includes at least one active tuning element movable to tune the isolation frequency thereof.

A compound helicopter includes a fuselage including a fuselage airframe, a translational thrust system coupled to the fuselage airframe and a pylon assembly subject to vibration. The pylon assembly includes a transmission and a rotor system having a main rotor assembly. The compound helicopter also includes a main rotor vibration isolation system including a plurality of augmented liquid inertia vibration eliminator units each having an isolation frequency and each coupled between the fuselage airframe and the pylon assembly to reduce transmission of the pylon assembly vibration to the fuselage airframe at the isolation frequency. Each augmented liquid inertia vibration eliminator unit includes at least one active tuning element movable to tune the isolation frequency thereof.

A mechanical power transmission that pivots about an axis to vary an angle between an input shaft and an output shaft. The mechanical power transmission includes an input gear having an input shaft that couples to a drive shaft, an output gear having an output shaft that couples to a tail rotor, a first intermediate gear rotationally coupled to the input gear, and a second intermediate gear rotationally coupled to the output gear. The mechanical power transmission further comprises a shaft that mechanically couples the first intermediate gear with the second intermediate gear, where a centerline of the shaft is coincident with the axis.